A. M. S. Smith, Sz. Csizmadia, V. Van Grootel, M. Lendl, C. M. Persson, G. Olofsson, D. Ehrenreich, M. N. Günther, A. Heitzmann, S. C. C. Barros, A. Bonfanti, A. Brandeker, J. Cabrera, O. Demangeon, L. Fossati, J. -. Harre, M. J. Hooton, S. Hoyer, S. Kalman, S. Salmon, S. G. Sousa, G. M. Szabó, T. G. Wilson, Y. Alibert, R. Alonso, J. Asquier, T. Bárczy, D. Barrado, W. Baumjohann, W. Benz, N. Billot, L. Borsato, C. H. Broeg, A. Collier Cameron, A. C. M. Correia, P. E. Cubillos, M. B. Davies, M. Deleuil, A. Deline, B.-O. Demory, A. Derekas, B. Edwards, J. A. Egger, A. Erikson, A. Fortier, M. Fridlund, D. Gandolfi, K. Gazeas, M. Gillon, M. Güdel, J. Hasiba, C. Helling, K. G. Isaak, L. L. Kiss, J. Korth, K. W. F. Lam, J. Laskar, A. Lecavelier Des Etangs, D. Magrin, P. F. L. Maxted, B. Merín, C. Mordasini, V. Nascimbeni, R. Ottensamer, I. Pagano, E. Pallé, G. Peter, D. Piazza, G. Piotto, D. Pollacco, D. Queloz, R. Ragazzoni, N. Rando, H. Rauer, I. Ribas, N. C. Santos, G. Scandariato, D. Ségransan, A. E. Simon, M. Stalport, S. Sulis, S. Udry, S. Ulmer-Moll, J. Venturini, E. Villaver, V. Viotto, I. Walter, N. A. Walton, S. Wolf
Abstract
Aims. We aim to observe the transits and occultations of WASP-33 b, which orbits a rapidly rotating δ Scuti pulsator, with the goal of measuring the orbital obliquity via the gravity-darkening effect, and constraining the geometric albedo via the occultation depth.
Methods. We observed four transits and four occultations with CHEOPS, and employ a variety of techniques to remove the effects of the stellar pulsations from the light curves, as well as the usual CHEOPS systematic effects. We also performed a comprehensive analysis of low-resolution spectral and Gaia data to re-determine the stellar properties of WASP-33.
Results. We measure an orbital obliquity 111.3−0.7+0.2 degrees, which is consistent with previous measurements made via Doppler tomography. We also measure the planetary impact parameter, and confirm that this parameter is undergoing rapid secular evolution as a result of nodal precession of the planetary orbit. This precession allows us to determine the second-order fluid Love number of the star, which we find agrees well with the predictions of theoretical stellar models. We are unable to robustly measure a unique value of the occultation depth, and emphasise the need for long-baseline observations to better measure the pulsation periods.
Keywords
planets and satellites: dynamical evolution and stability / planets and satellites: fundamental parameters / planets and satellites: gaseous planets / planets and satellites: individual: WASP-33 b / stars: oscillations – stars: individual: WASP-33
Astronomy & Astrophysics
Volume 693, Article Number A128, Number of pages 18
2025 January
